Peter J. Yim PhD, Presenter: Grant, Siemens AG

John L. Nosher MD, Abstract Co-Author: Nothing to Disclose

Haroon Rahimi, Abstract Co-Author: Nothing to Disclose

Anthony Burgos MD, Abstract Co-Author: Nothing to Disclose

Ihab Haddadin MD, Abstract Co-Author: Nothing to Disclose

The accuracy of computed tomographic angiography (CTA) for grading the severity of arterial stenoses is reduced in calcified arteries. The aim of this study is to evaluate the feasibility of dual-energy subtraction computed tomographic angiography (DESCTA) that is designed for suppression of calcification.

DESCTA was evaluated in a calcified-artery phantom. The phantom consisted of four thin-walled tubes ranging in diameter from 2.5 to 7.5 mm. Each tube was surrounded by plaque material in an eccentric conformation. The tubes were filled with a solution of iodinated contrast media with an iodine density of 11 mg/ml. The plaque material was a composite of petrolatum and calcium carbonate with a calcium density of 180 mg/ml. DESCTA was obtained on a computed tomography (CT) system with dual-source capability. Image acquisition included the use of tube voltages of 80 and 140 kvp. Tube current of the 140 kvp source was the same as used for a conventional CTA acquisition, after adjusting for the phantom geometry. The ratio of the tube current of the 80 kvp source to that of the 140 kvp source was 4.2. Image reconstruction was performed at 2.0-mm slice thickness.  DESCTA was obtained through a linear combination of the low- and high-energy CT. The linear combination included a scaling of the high-energy CT followed by subtraction from the low-energy CT. The scale factor was the ratio of the maximum image intensity in the calcification in the low-energy CT to that at the same point in the high-energy CT. Image processing was performed in MIPAV (NIH).  Measurements of luminal diameter were made by three readers. Analysis of the accuracy of DESCTA was performed using a zero-offset-constrained linear regression model.

Measurements of luminal diameter in DESCTA were strongly predictive of caliper measurements (p = 0.010). The standard error of the estimate was 1.0 mm. No significant differences in the measurement of diameter were observed between measurements in calcified and non-calcified segments (p = 0.70).

DESCTA was found to be a promising method for imaging of calcified arteries. Further evaluation under more realistic conditions is needed.

This study provides strong evidence of the feasibility of dual-energy subtraction CTA and represents the first step towards a novel methodology for the evaluation of calcified arteries.

Yim, P, Nosher, J, Rahimi, H, Burgos, A, Haddadin, I, Dual-Energy Subtraction Computed Tomographic Angiography in Calcified Arteries: A Feasibility Study.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6009170.html